Currently in the nonwoven industry, with the exception of the pulp and super absorbent materials, disposable articles tend to be made of materials that are hydrophobic in nature. Water dispersible thermoplastic materials are gaining greater popularity as disposable article converters desire to incorporate hydrophilic features into their products.
WO 95/18191 teaches a water-dissipatable or dispersible adhesive composition useful in forming paper articles and other products that can be recycled through repulping in both neutral and alkaline media. The water-dispersible adhesive composition is preferably a hot melt adhesive that is a low molecular weight, branched copolyester containing a sulfonomer. Such polymers have recently become available under the tradename "Eastman AQ" copolyesters.
The "Eastman AQ" copolyesters are currently available in three experimental viscosity grades and one commercial viscosity grade, namely Eastman AQ 1350. Table I depicts typical physical property data of the neat copolyesters. The copolyesters depicted in Table I are believed to be substantially linear in structure. In general, the neat copolyesters exhibits several deficiencies including cold flowability of the low molecular weight copolyesters, as well as poor sprayability, poor thermal stability and reduced water dispersibility of the higher viscosity materials.
The applicants have found that the "Eastman AQ" copolyesters, as well as similar water responsive copolyesters, have great utility in the nonwoven converting industry. When properly formulated, the disadvantages of the neat polyester can be overcome. Furthermore, the applicants discovered that it is possible to control the degree of water responsiveness such that the formulated adhesives may be useful for incorporating hydrophilic features into the substrates as well as the adhesives present yet not necessarily be water dispersible at one end of the spectrum, to using water dispersible copolyesters as a base raw material to make in-line substrates as well as adhesives to manufacture a completely flushable sanitary napkin or diaper at the other extreme.
When properly formulated, water responsive copolyesters are also suitable for adhesives compositions that improve acquisition and fluid management. Such adhesive compositions may be present to stabilize the core, improve the wicking of the core, for fixation of super absorbent polymers, or as a hydrophilic coating on a nonwoven. Additionally, water dispersible copolyesters have utility in formulating more traditional adhesive applications for construction, elastic attachment, or as garment attachment adhesives for securing a feminine napkin to an undergarment.